This invention relates to venous drainage catheters, and especially to multi stage venous catheters.
A venous drainage catheter is used during cardiac surgery to remove blood from or near the patient's venous system. The removed blood is conducted to heart lung equipment which treats the blood, e.g., by removing carbon dioxide, infusing oxygen, heating, cooling, etc. before returning the treated blood to the patient.
The catheter includes drainage openings for conducting blood from the right atrium and/or vena cava.
During introduction of the catheter into the patient's body, or during subsequent adjustment of the catheter, the catheter may become bent, which tends to produce kinking that will undesirably reduce blood flow. Consequently, it is conventional to reinforce the catheter to prevent such bending.
For example, U.S. Pat. No. 4,639,252 discloses a catheter reinforcement in the form of a cylindrical plastic sleeve embedded in the plastic body of the catheter, with drainage openings punched through the body and sleeve.
In U.S. Pat. No. 5,769,828 a catheter reinforcement is disclosed which is comprised of axially extending beams spaced circumferentially apart. Alternating pairs of adjacent beams are interconnected at their forward or rearward ends by a circumferentially extending connecting piece. There is thus provided a reinforcement which is capable of being expanded over a larger diameter. Drainage holes are punched through the body of the catheter in spaces formed between adjacent beams.
Reinforcement for a catheter disclosed in U.S. Pat. No. 6,152,911 comprises a coil spring defining spaces between successive turns of the coil. Drainage openings are formed in those spaces.
Common to each of the above-described reinforced catheters is the creation of a uniform reinforcement along a section of the catheter. Although such uniform reinforcement resists the tendency for kinking to occur in that section, it also resists the bending of the catheter thereby considerably limiting the flexibility of the section.
It would be desirable to provide a venous drainage catheter with reinforcement which produces minimal resistance to bending thereof while effectively resisting kinking.